Wireless communication systems are widely deployed to provide various telecommunication services such as telephony, video, data, messaging, and broadcasts. Typical wireless communication systems may employ multiple-access technologies capable of supporting communication with multiple users by sharing available system resources (e.g., bandwidth, transmit power). Examples of such multiple-access technologies include Long Term Evolution (LTE) systems, code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, single-carrier frequency division multiple access (SC-FDMA) systems, and time division synchronous code division multiple access (TD-SCDMA) systems.
In some examples, a wireless multiple-access communication system may include a number of base stations, each simultaneously supporting communication for multiple communication devices, otherwise known as user equipment (UEs). In LTE or LTE-A network, a set of one or more base stations may define an eNodeB (eNB). In other examples (e.g., in a next generation or 5G network), a wireless multiple access communication system may include a number of distributed units (DUs) (e.g., edge units (EUs), edge nodes (ENs), radio heads (RHs), smart radio heads (SRHs), transmission reception points (TRPs), etc.) in communication with a number of central units (CUs) (e.g., central nodes (CNs), access node controllers (ANCs), etc.), where a set of one or more distributed units, in communication with a central unit, may define an access node (e.g., a new radio base station (NR BS), a new radio node-B (NR NB), a network node, 5G NB, gNB, etc.). A base station or DU may communicate with a set of UEs on downlink channels (e.g., for transmissions from a base station or to a UE) and uplink channels (e.g., for transmissions from a UE to a base station or distributed unit).
These multiple access technologies have been adopted in various telecommunication standards to provide a common protocol that enables different wireless devices to communicate on a municipal, national, regional, and even global level. An example of an emerging telecommunication standard is new radio (NR), for example, 5G radio access. NR is a set of enhancements to the LTE mobile standard promulgated by Third Generation Partnership Project (3GPP). It is designed to better support mobile broadband Internet access by improving spectral efficiency, lowering costs, improving services, making use of new spectrum, and better integrating with other open standards using OFDMA with a cyclic prefix (CP) on the downlink (DL) and on the uplink (UL) as well as support beamforming, multiple-input multiple-output (MIMO) antenna technology, and carrier aggregation.
However, as the demand for mobile broadband access continues to increase, there exists a need for further improvements in NR technology. Preferably, these improvements should be applicable to other multi-access technologies and the telecommunication standards that employ these technologies.
Certain designs provide long CRC (Cyclic Redundancy Check) protection for Code Block Group (CBG) level Acknowledgement (ACK)/Negative ACK (HACK) feedback and assume that the CBG ACK/NACK feedback from a UE is reliably received by the gNB. Thus, these designs do not consider error events in receiving the feedback at the gNB.
However, in 5th Generation (5G) New Radio (NR) design, there is either no CRC or the CRC is not long enough for CBG ACK/NACK feedback resulting in potential errors in receiving the CBG ACK/NACK feedback at the gNB. Thus, when a UE feeds back CBG ACK/NACK there may be a decoding error at the gNB receiving the feedback and the gNB may retransmit a wrong set of CBGs. For example, a UE may transmit CBG ACK/NACK feedback including NACKs for a set A of CBGs indicating that the CBGs in set A were not received correctly at the UE. The gNB however may incorrectly decode the feedback from the UE and retransmit a different set B of CBGs to the UE. This may lead the UE to combine Log Likelihood Ratios (LLRs) from CBGs in set B with LLRs from CBGs in set A from a previous transmission of CBGs in set A. This mismatch may result in a failure in decoding one or more set A CBGs